The present invention relates to manufacturing of amorphous metal objects, such as stators.
Multi-pole rotating electrical devices, such as motors and generators, are comprised of rotors and stators. AC motors rotate by producing a rotating magnetic field pattern in the stator that causes the rotor to follow the rotation of this field pattern. As the frequency varies, the speed of the rotor varies. To increase the speed of the motor, the frequency of the input source must be increased.
High frequency motors manufactured with the proper materials can be very efficient. For certain applications, like electric or hybrid cars, highly efficient electric motors are desirable.
The construction of stators for high frequency electric motors is problematic. Iron or steel stators are quite common in electric motors. However, at high frequencies, such as those greater than 400 Hz, iron or steel stators are no longer practical. The high frequency of the AC source increases the core losses of the iron or steel stator, reducing the overall efficiency of the motor. Additionally, at very high frequencies, the stator may become extremely hot and may cause motor failure.
For construction of stators used in high frequency electric motors, amorphous metal would be ideal. Amorphous metal is easy to magnetize and demagnetize, which means a stator made with amorphous metals would have low power loss, low temperature rise at high frequency, extremely fast magnetization (high permeability) and easy conversion of electrical to mechanical energy. A stator made of such an amorphous metal would generate less core losses and be able to operate at much higher frequencies, resulting in motors of exceptional efficiency and power density.
Amorphous metals are commercially produced as ribbon. An example of amorphous metal ribbon is Metglas®, manufactured by Honeywell, Inc. Amorphous metal ribbons are very thin and of varying width. Manufacturing components of amorphous metal ribbon requires winding the amorphous material into a shape and then heat processing the shape. Simple three dimensional shapes, such as toroids, can currently be constructed from amorphous metal ribbon.
However, a stator is not a simple three dimensional shape. The stator has numerous slots for accommodating motor coils milled into a general toroid structure. Manufacturing stators of amorphous metal ribbon presents challenges.
Attempts to create complex three dimensional configurations from amorphous metal ribbon have heretofore been commercially unsuccessful. Various manufacturing techniques have been attempted by industry such as but not limited to: wire electrical discharge machining, electrochemical creep grinding, conventional electrical discharge machining, cutting, stamping, acid etching and fine blanking. None thus far have proven satisfactory for reasons such as cost-effectiveness, manufacturing repeatability, or process cycle time.
This inability to fabricate complex three dimensional shapes from amorphous ribbon has been the significant impediment to producing high efficiency axial flux motors and generators.
A method to produce stators from amorphous ribbon in a cost effective, end use functional, high volume capable method that also provides substantial design flexibility for end use requirements is highly desirable.